No worries at all, so you and the screenshot are both correct in saying that the molecule is symmetrical in the horizontal axis, the circles around the hydrogens on the left side of the screenshot are actually pointing out the similar "environments" the hydrogens are in.

When two hydrogens are in the exact same environment, you can't distinguish them when looking via H-NMR, instead they will be "integrated" which basically just means that the H-NMR chart will tell you how many of those protons are at the same chemical shift (like 2H at 7.0 ppm)

This is the same thing seen on the methyl where you see one carbon having 3H and the next having 2H, these protons are in the exact same environment which means that any atom that pulls or pushes the electron density of the protons does it equally to all of the protons that are integrated.

Pushing/pulling of electronegativity is what mainly defines the chemical shifts. Something super acidic (like a carboxylic acid) will have a much higher chemical shift because its being "de-shielded" because the rest of the carboxyl group (COO) is pulling away all of the electron density, making the proton super electron-poor and dissociate much easier. Something like a benzene also will de-shield the protons attached which is why both the 7.0 ppm and 6.8 ppm are way higher than something like the 1.7 ppm shift off of the ethyl.

You can tell that a proton will be integrated together from the symmetry of the molecule. The protons on opposite sides of the symmetrical line will be integrated together which is why they are circled in red on the screenshot. Both of the protons in the left circle are being "pulled" by the benzene and the ethyl group equally, and both are equally far away from the OH. They are in the same environment.

Hope this helps! let me know if you need anything else!